Repair-screw for boilers.



L. A. CORNELIUS. REPAIR SGREW FOR BOILERS. APPLIOATION FILED SEPT.30,1908.

1,066,253. Pate nted July 1, 1913.

ATTORNEY.

- in the accompanying drawing,

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nnram-scnnw ron. BOILERS.

Specification of Letters Patent.

Patented July 1, 1913.

Application filed September 30, 1908. Serial No. 455,499.

small breaks, openings or fractures in steam boilers, or in other similar metal shells. It is common to find in such metal shells, especially those which have to withstand a high degree of atmospheric or other pressure upon. one side, small breaks or openings, or weak spots causing'danger of such breaks; These weak spots or openings may come from corrosion at any particular polnt, or from someimperfect spot in the original metal, or from any other local cause; and they may be, and frequently are, so small that the taking out and replacing of a section of the shell, or even the attaching of a patch by any riveting or welding process, calls for an expenditure of time and labor which can not be economically devoted to that purpose. By the use of this device I can repair such an opening or break or weak spot at slight ex ense, and with a little time. I accom-' phsh this result by the construction shown in which Figure 1 is a side plan-view of my device. Fig. 2 is a side elevation of the same from a difierent angle. Fig. 3 is a top plan view of the same. Fig. 4 is a cross-section of the same on the line w-w of Fig. 2.

The device is intended to screw into the opening or fracture which is to be closed. It is practically necessary, however, that it should be driven for a short distance, and for this purpose the lower end of the device is made tapering with a sharper taper than that of the body of the screw, and having the outer edges of the leader threads which run down on this point out ofi so that they will not be turned by the driving operation, but, nevertheless, may be measurably operative when the turning motion is commenced.

Experience has demonstrated that it is impossible to turn an ordinary screwthreaded stem into a metal seat likea metal boiler shell, unless with the aid of some experi pedient other than the ordinary screwthread; and for this purpose it is necessary to provide a cutting edge, as in a tap. The ordinary tap, or a device of this character in the form of the ordinary tap, would be inefficient, since, although its several cutting edges, usually four, would efficiently cut a thread for receiving the thread on the stem, there would not be sufficient of the unbroken threaded portion to give a sufiiciently firm hold or grip of the metal in which it is inserted, so that the stem would be blown or forced out of position by the pressure of the gas or liquid contained in the receptacle. Even if the cutting edges in the form of the ordinary tap were reduced to two there would still be, upon opposite sides of the device, considerable portions which did not grip, through the screw-thread, the adjacent surrounding metal, and the device would therefore be materially weakened and practically ineflicient.

I have found that by cutting in the side of the screw-threaded stem an opening or groove of substantially the relative size and shape indicated in Fig. 2 and shown in cross-section in F g. 3, I provide at the point 4 a sufiicient cutting edge which willcut threads in the surrounding metal for the following screw-threads upon the stem;

and at the same time the open space or groove between edges 4 and 5 is sufiiciently wide and of suflicient depth so that the surrounding metal will enter the same far enough to make the cutting edge 4 operative, and at the same time is not sufficiently extensive anddoes not remove enough of the hery of the screw-thread to prevent at all times an engagement between the screwthreaded stem and the surrounding metal practically as strong as if the groove did not exist. As indicated in Fig. 2, this groove may be so out as to extend nearly or quite to the extreme upper or outer end or edge of the threaded stem, since, even though it might make a passage for the steam nearly through the shell, the outer end would be absolutely and efiiciently closed by the pack ing which is held in position by the screw head. Upon the inner or lower end I extend this groove past the threads of full depth, and down nearly to the extreme point of the device, intersecting also the threads which have their edges cut away. By this construction the cutting edge 4 is carried closeto the point, and its operation as a tap may begin at any time, instead of compelling the creation, by driving, of a hole approximately as large as the main body of the screw stem, as would be the case if the driving point was without this groove and extended in plain form up to the full-depth tapping threads.

- Upon the upper or outer end of the stem I provide a head 6. This is practically circular in form, butits edge is provided with a suitable number, as six, of smooth faces 7 7 whereby it may be gripped by a wrench or suitable instrument for turning. It is 'also provided, on its upper face, with the boss or projection 8, intended and especially adapted to receive the blows of a driving instrument during the first part of the insertion process. The device may thus be driven against great resistance and without marring or injuring, or indeed touching the circular projecting head 6, thusavoiding any danger of distorting such head by a driving blow, and further insuring that the driving blow shall be centrally received.

9 is a packing washer of suitable material surrounding the upper or outer end of the threaded stem. When a small hole, or fracture, or weak s ot suitable for repairing by this device, is eveloped, the plug will first be driven for a short distance. The plug will then be turned down into position through the grip of a wrench upon the smooth faces 7 of the head 6, the plug operating both as a tap and as a screw until it is i turned fully into position, when the under surface of the head 6 will bear upon the washer 9, clamping this washer very firmly against the outer surface of the metal shell to be repaired, and thus efliciently and securely closing and repairing the spot requiring such treatment.

It is apparent that by avoiding any upwardly projecting portion beyond the stem or head and by providing for a wrench grip upon the edges of the head itself, I avoid any considerable projection'beyond the body of the shell repaired, and the repair work is neat and convenient as well as efficient and very inexpensive.

It will be observed that the groove which provides the cutting edge in the form shown in the drawing, has one long side and one short side; that the short side is substantially radial of the screw stem and that the angle between the two sides issubstantially a right angle. The short side of this groove should not depart substantially from the radial position; that is to say, it should not incline in one direction far enough to undercut and weaken the cutting edge, nor in the other direction farenough to make the 'cut- .ting edge oblique and not sharp enough. Making the short side of the groove in this form, and making the groove approximately right angled, insures that the long side shall be sufficiently proportionate to give room for the surrounding metal to shrink or crowd into the groove so that it may be cut by the edge 4, but not so disproportionately long as materially to weaken the strength of the stem or the grip of the screw-thread upon the surrounding metal.

Having thus described my invention, what I claim to have invented, and desire to secure by Letters Patent, is

A repair screw for boilers adapted for insertion into the wall of the boiler, first by a driving, and then by a turning act-ion having a shank provided with a pointed extremity and with a head, and having between the extremity and the head a tapering outline which from a point near the center of the shank to the pointed extremity is of greater degree than from the said point to the head, the shank being provided with threads and the threads in the portion which has the greater degree of taper having their apices gradually flattened or cut away throughout their extent as they approach the pointed extremity and yet measurably operative to engage the part in which the screw is inserted, the shank having also but a single longitudinal recess interrupting the threads and extending'from a point closely adjacent the head to a point on the extremity and beyond the threads, the recess having a radially extending face provided with a longitudinal cutting edge and having also a face which extends at a substantial right angle from the radial face, the head being formed to receive the blow of a hammer and also for engagement by a wrench or its equivalent.

- In testimony whereof I have hereunto set my hand in presence of two subscribing witnes'ses. LOUIS A. CORNELIUS.

Witnesses:

MARY S. Tooxna, CHAS.-M. WILSON. 

